Lubricating oil composition

ABSTRACT

The present invention relates to a lubricating oil composition containing: a base oil, (A) a benzotriazole derivative having a particular structure, (B) an epoxy compound, and (C) an ashless friction modifier, the ashless friction modifier (C) being contained in an amount of 0.20% by mass or more based on the total amount of the lubricating oil composition.

TECHNICAL FIELD

The present invention relates to a lubricating oil composition.

BACKGROUND ART

At the present time, the global environmental regulation is becoming severer, and in particular, the circumstances surrounding automobiles are becoming unilaterally severer in fuel consumption regulations, exhaust gas regulations, and the like. The background of the circumstances includes the environmental problems, such as the global warming, and the resource protection caused by concerns about depletion of the oil resources. It is considered that the fuel consumption saving is being advanced due to the aforementioned factors. For the fuel consumption saving of automobiles, what is important includes an improvement of an engine oil, such as reduction of the viscosity of an engine oil and addition of a favorable friction modifier, for preventing the frictional loss in an engine, in addition to the improvement of an automobile itself, such as reduction of the weight of an automobile and improvement of an engine. However, the reduction of the viscosity of the engine oil may be a factor increasing the friction in various members in the engine. For reducing the frictional loss associated with the reduction of the viscosity and for preventing wear, a friction modifier, an extreme pressure agent, and the like are becoming important more than ever.

An iron based material and an aluminum based material have been mainly used for a sliding material of an engine and the like, and a wide variety of materials including aluminum and copper without limiting to an iron based material has been used for a material of a sliding member of a main bearing, a con rod bearing, and the like, for example, a bearing metal. Although there is an orientation that the use of tin, lead, and the like is restricted, these elements are being contained in some materials. The copper- or lead-containing metal materials undergo less fatigue phenomena as an excellent feature thereof, but are liable to be corroded as a defect thereof. Accordingly, the lubricating oil and the additives are demanded to have a corrosion resistance for the metal materials, in addition to the reduction of frictional loss and the prevention of wear.

The lubricating oil is demanded to have various capabilities as described above, and various additives are generally added thereto for satisfying the various cap abilities.

For example, PTL 1 describes a lubricating oil composition for an internal combustion engine, containing a lubricant base oil having contained therein a particular molybdenum oxysulfide dithiocarbamate, an acid amide compound, a fatty acid partial ester compound and/or an aliphatic amine compound, and a particular benzotriazole derivative, each in particular contents.

PTL 2 describes a fuel consumption saving type engine oil composition containing a lubricant base oil having contained therein an organic molybdenum compound in an amount of 0.02% by mass or more in terms of molybdenum (Mo) amount and an alicyclic epoxy compound.

PTL 3 describes a lubricating oil composition containing a lubricant base oil having contained therein a particular phosphorus compound and an epoxy compound each in particular contents.

PTL 4 describes a lubricating oil composition containing a lubricant base oil having contained therein a fatty acid partial ester compound, an aliphatic amine compound and/or an acid amide compound, a particular benzotriazole derivative, and a particular succinimide compound, each in particular amounts.

CITATION LIST Patent Literatures

PTL 1: JP 2008-106199 A

PTL 2: WO 2011/161982

PTL 3: JP 2012-201807 A

PTL 4: WO 2008/047550

SUMMARY OF INVENTION Technical Problem

However, the molybdenum oxysulfide dithiocarbamate (which may be hereinafter referred to as “MoDTC”) used in PTLs 1 and 2 is excellent in friction reducing effect, but has a concern about corrosiveness to copper. For example, PTL 2 describes in Comparative Example 2 thereof that significant corrosion of copper occurs in the case where MoDTC is blended.

For suppressing the corrosion of copper, PTLs shown above use a particular benzotriazole derivative, but it has been known that the use of the benzotriazole derivative is insufficient in effect of suppressing corrosion of lead, and for example, PTL 2 describes in Comparative Example 4 thereof that elution of lead is increased when the benzotriazole derivative is blended in a large amount.

For suppressing the corrosion of lead, PTLs 2 and 3 use an epoxy compound, but there has been no study for the use thereof in a lubricating oil composition using an ashless friction modifier as a friction modifier.

Furthermore, in the case where an ashless friction modifier is used instead of MoDTC, the content of the ashless friction modifier is necessarily increased for providing a sufficient friction reducing effect, and the use of the ashless friction modifier causes a concern about corrosiveness to lead. For example, PTL 4 describes a lubricating oil composition containing an ashless friction modifier and a particular benzotriazole derivative, but there is room for improvement in corrosion suppressing effect of copper and lead.

As described above, a lubricating oil composition is demanded to have an excellent friction reducing effect, but in the case where an ashless friction modifier is used as a friction modifier, it is necessary to achieve both a corrosion suppressing effect of copper and a corrosion suppressing effect of lead simultaneously, in addition to an excellent friction reducing effect.

The present invention has been made in view of the aforementioned circumstances, and an object of the present invention is to provide a lubricating oil composition using an ashless friction modifier, the lubricating oil composition being excellent in friction reducing effect and also being excellent in corrosion suppressing effects of copper and lead.

Solution to Problem

As a result of accumulated studies made by the present inventors, it has been found that the problem can be solved by blending a benzotriazole derivative having a particular structure and an epoxy compound with a base oil, and blending an ashless friction modifier therewith in a particular amount. The present invention has been completed based on the knowledge. Specifically, the present invention provides the following items [1] and [2].

[1] A lubricating oil composition containing:

a base oil,

(A) a benzotriazole derivative represented by the general formula (I):

wherein R¹ represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 9 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom; and R² represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 16 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom,

(B) an epoxy compound, and

(C) an ashless friction modifier,

the ashless friction modifier (C) being contained in an amount of 0.20% by mass or more based on the total amount of the lubricating oil composition.

[2] A lubricating method including using the lubricating oil composition according to the item [1] to a member containing copper or lead.

Advantageous Effects of Invention

According to the present invention, a lubricating oil composition using an ashless friction modifier, excellent in friction reducing effect and also excellent in corrosion suppressing effects of copper and lead can be provided.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention will be described in detail below.

[Lubricating Oil Composition]

A lubricating oil composition according to one embodiment of the present invention contains: a base oil, (A) a benzotriazole derivative represented by the general formula (I):

wherein in the general formula (I), R¹ represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 9 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom; and R² represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 16 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom, (B) an epoxy compound, and (C) an ashless friction modifier, and the ashless friction modifier (C) is contained in an amount of 0.20% by mass or more based on the total amount of the lubricating oil composition.

The lubricating oil composition according to one embodiment of the present invention contains the ashless friction modifier (C) as a friction modifier in an amount of 0.20% by mass or more based on the total amount of the lubricating oil composition, and thus has an excellent friction reducing effect. Furthermore, the lubricating oil composition contains the ashless friction modifier (C) in a large amount, but contains the benzotriazole derivative (A) represented by the general formula (I) and the epoxy compound (B), and thus has excellent corrosion suppressing effects of copper and lead simultaneously.

These effects are not such ones that are obtained from the simple combination of respective effects expected from the use of the benzotriazole derivative and the epoxy compound separately.

The components constituting the lubricating oil composition according to one embodiment of the present invention will be described below.

<Base Oil>

The base oil used in the lubricating oil composition is not particularly limited, and an arbitrary material appropriately selected from mineral oils and synthetic oils that have been used as a base oil of a lubricating oil may be used.

Examples of the mineral oil include a mineral oil that is produced in such a manner that an atmospheric residual oil obtained by distilling a crude oil under an atmospheric pressure is distilled under reduced pressure to provide a lubricating oil fraction, which is purified by performing one or more treatment of solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, and the like, and a base oil produced through isomerization of wax or GTL (gas-to-liquid) wax.

Examples of the synthetic oil include a poly-α-olefin, such as polybutene and a homopolymer or copolymer of an α-olefin (such as an ethylene-α-olefin copolymer); various esters, such as a polyol ester, a dibasic acid ester, and a phosphate ester; various ethers, such as a polyphenyl ether; a polyglycol; an alkylbenzene; and an alkylnaphthalene. Among these synthetic oils, a poly-α-olefin and a polyol ester are preferred.

In one embodiment of the present invention, the mineral oil may be used alone or as a combination of two or more kinds thereof as the base oil. The synthetic oil may be used alone or as a combination of two or more kinds thereof. One or more kinds of the mineral oil and one or more kinds of the synthetic oil may be used in combination.

The content of the base oil is generally 65% by mass or more, preferably 70% by mass or more, and more preferably 75% by mass or more, and is preferably 97% by mass or less, and more preferably 95% by mass or less, based on the total amount of the lubricating oil composition.

While the viscosity of the base oil is not particularly limited, the kinetic viscosity at 100° C. thereof is preferably in a range of 2 mm²/s or more and 30 mm²/s or less, more preferably 3 mm²/s or more and 15 mm²/s or less, and further preferably 3 mm²/s or more and 10 mm²/s or less.

When the kinetic viscosity at 100° C. is 2 mm²/s or more, the evaporation loss may be small, and when the kinetic viscosity at 100° C. is 30 mm²/s or less, the power loss due to the viscosity resistance may be suppressed to provide a fuel consumption improving effect. The value of the kinetic viscosity at 100° C. is measured by the method described in the examples later.

The viscosity index of the base oil is preferably 70 or more, more preferably 100 or more, and further preferably 120 or more. The base oil that has a viscosity index of 70 or more may have a small change in viscosity on change in temperature.

When the viscosity index of the base oil is in the range, the viscosity characteristics of the lubricating oil composition can be readily improved. The viscosity index is an index that is measured by the method described in the examples later.

The base oil used preferably has an aromatic content (% C_(A)) by ring analysis of 3.0 or less and a sulfur content of 50 ppm by mass or less. The % C_(A) by ring analysis herein means a ratio (percentage) of an aromatic component that is calculated by the ring analysis n-d-M method. The sulfur content is a value that is measured according to JIS K2541.

The base oil that has a % C_(A) of 3.0 or less and a sulfur content of 50 ppm by mass or less may have good oxidation stability, and thereby the increase of the acid number and the formation of sludge may be suppressed, and a lubricating oil composition having less corrosiveness to a metal can be provided.

The % C_(A) is more preferably 1.0 or less, further preferably 0.5 or less, and still further preferably 0.1 or less. The sulfur content is more preferably 10 ppm by mass or less, further preferably 5 ppm by mass or less, and still further preferably 2 ppm by mass or less.

The base oil used preferably has a paraffin content (% C_(P)) by ring analysis of 65 or more, more preferably 70 or more, and further preferably 75 or more. When the paraffin content is 65 or more, the base oil may have good oxidation stability. The % C_(P) by ring analysis herein means a ratio (percentage) of a paraffin component that is calculated by the ring analysis n-d-M method.

The NOACK value of the base oil is preferably 15.0% by mass or less, more preferably 14.0% by mass or less, and further preferably 13.0% by mass or less.

The value of % C_(A), the value of % C_(P), the sulfur content, and the NOACK value are values that are measured according to the methods described in the examples later.

<Benzotriazole Derivative (A) Represented by General Formula (I)>

The lubricating oil composition contains the benzotriazole derivative (A) represented by the general formula (I) (which may be hereinafter referred simply to a “component (A)”). With the component (A) contained, a lubricating oil composition that contains an ashless friction modifier and is excellent in corrosion suppressing effect of copper can be provided.

The component (A) used in the lubricating oil composition is represented by the following general formula (I).

In the general formula (I), R¹ represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 9 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom; and R² represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 16 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom.

R¹ preferably represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 5 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom, more preferably represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 3 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom, and further preferably represents a methyl group or a hydrogen atom, from the standpoint of the achievement of a lubricating oil composition excellent in corrosion suppressing effect of copper.

R² preferably represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 8 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom, more preferably represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 5 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom, further preferably represents a methyl group or a hydrogen atom, and still further preferably represents a hydrogen atom, from the standpoint of the achievement of a lubricating oil composition excellent in corrosion suppressing effects of copper and lead simultaneously in the case where the component (B) described later is used in combination.

Accordingly, the component (A) is further preferably one represented by the general formula (I) where R¹ represents a methyl group or a hydrogen atom and R² represents a hydrogen atom.

The content of the component (A) is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, further preferably 0.03% by mass or more, and still further preferably 0.05% by mass or more, based on the total amount of the lubricating oil composition, from the standpoint of the enhancement of the corrosion suppressing effect of copper. The content of the component (A) is preferably 0.15% by mass or less, more preferably 0.10% by mass or less, and further preferably 0.07% by mass or less, based on the total amount of the lubricating oil composition, from the standpoint of the solubility.

As the component (A), the benzotriazole derivatives represented by the general formula (I) may be used alone, and two or more kinds of the benzotriazole derivatives represented by the general formula (I) having different structures may be used in combination. The preferred ranges of the total content in the case where two or more kinds of the components (A) are used in combination are the same as the preferred ranges in the case where the component (A) is used alone.

By using the component (A) in combination of the component (B) described later, not only the elution of copper can be simply suppressed, but also a better lead elution suppressing effect than the lead elution suppressing effect obtained in the case where the component (B) is used alone can be obtained through the synergistic effect.

<Epoxy Compound (B)>

The lubricating oil composition contains the epoxy compound (B) (which may be hereinafter referred simply to a “component (B)”). With the component (B) contained, a lubricating oil composition excellent in corrosion suppressing effect of lead can be provided although the component (A) is contained therein.

Examples of the component (B) include a compound having at least one epoxy group in the molecule, and preferably a compound having two or more epoxy groups in the molecule.

Examples of the component (B) include an epoxy compound having a number of carbon atoms of 3 or more having a linear-chain or branched-chain alkyl group (1,2-epoxyalkane), a glycidyl ester type epoxy compound, and an alicyclic epoxy compound. The component (B) is preferably one or more selected from the group consisting of an epoxy compound having a linear-chain or branched-chain alkyl group having a number of carbon atoms of 3 or more and 26 or less (1,2-epoxyalkane) and an alicyclic epoxy compound, and more preferably an alicyclic epoxy compound.

The number of carbon atoms of the epoxy compound having a linear-chain or branched-chain alkyl group having a number of carbon atoms of 3 or more and 26 or less (epoxyalkane) is preferably 10 or more, more preferably 12 or more, and further preferably 14 or more. The number of carbon atoms thereof is preferably 22 or less, more preferably 20 or less, and further preferably 18 or less.

Examples of the epoxyalkane having a linear-chain alkyl group having a number of carbon atoms of 3 or more and 26 or less include 1,2-epoxypropane, 1,2-epoxybutane, 1,2-epoxypentane, 1, 2-epoxyhexane, 1,2-epoxyheptane, 1,2-epoxyoctane, 1,2-epoxynonane, 1,2-epoxydecane, 1,2-epoxyundecane, 1,2-epoxydodecane, 1,2-epoxytridecane, 1,2-epoxytetradecane, 1,2-epoxypentadecane, 1,2-epoxyhexadecane, 1,2-epoxyheptadecane, 1,2-epoxyoctadecane, 1,2-epoxynonadecane, 1,2-epoxyicosane, 1,2-epoxyhenicosane, 1,2-epoxydocosane, 1,2-epoxytricosane, 1,2-epoxytetracosane, 1,2-epoxypentacosane, and 1,2-epoxyhxacosane.

Examples of the epoxyalkane having a branched-chain alkyl group having a number of carbon atoms of 3 or more and 26 or less include compounds each having the aforementioned linear-chain alkyl group having, bonded to the alkyl chain moiety having the number of carbon atoms thereof, an alkyl group having a number of carbon atoms within a range that satisfies the number of carbon atoms.

Preferred examples of the glycidyl ester type epoxy compound include a phenyl glycidyl ester, an alkyl glycidyl ester, and an alkenyl glycidyl ester, and examples thereof include glycidyl benzoate, glycidyl 2,2-dimethyloctanoate, glycidyl acrylate, and glycidyl methacrylate.

Preferred examples of the alicyclic epoxy compound include an alicyclic epoxy compound having a number of carbon atoms of 3 or more and 18 or less, and more preferably a number of carbon atoms of 5 or more and 16 or less.

Examples of the alicyclic epoxy compound include 1,2-epoxycyclopropane, 1,2-epoxycyclobutane, 1,2-epoxycyclopentane, 1,2-epoxycyclohexane, 1,2-epoxycycloheptane, 1,2-epoxycyclooctane, 1,2-epoxycyclononane, 1,2-epoxycyclodecane, 1,2-epoxycyclododecane, and 1,2-epoxynorbornane. Examples thereof also include an alkylated or alkenylated epoxycycloalkane having one or more alkyl group or alkenyl group bonded to the carbon atom of the alicyclic moiety, such as 2-(7-oxabicyclo[4.1.0]hept-3-yl)-spiro(1,3-dioxane-5,3′-[7]oxabicyclo[4.1.0]heptane, 4-(1′-methylepoxyethyl)-1,2-epoxy-2-methylcyclohexane, and 4-epoxyethyl-1,2-epoxycyclohexane.

Preferred examples of the alicyclic epoxy compound also include an ether compound having one or more aliphatic or aromatic alkoxy group bonded to the carbon atom of the alicyclic moiety, an imide compound and a bisimide compound each having one or more imide group bonded to the carbon atom of the alicyclic moiety, and an amide compound having one or more amide group bonded to the carbon atom of the alicyclic moiety, and more preferred examples thereof include an ester compound having one or more carboxy group bonded to the carbon atom of the alicyclic moiety.

More preferred examples of the alicyclic epoxy compound include a compound having two epoxidized cycloalkanes. Preferred examples of the compound having two epoxidized cycloalkanes include a 3,4-epoxycycloalkyl-3,4-epoxycycloalkylcarboxylate (in which the alkyl groups each have a number of carbon atoms of 3 or more and 12 or less), and more preferred examples thereof include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate.

The content of the component (B) is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, further preferably 0.20% by mass or more, and still further preferably 0.30% by mass or more, based on the total amount of the lubricating oil composition, from the standpoint of the enhancement of the corrosion suppressing effect of lead. The content thereof is preferably 1.00% by mass or less, more preferably 0.70% by mass or less, and further preferably 0.50% by mass or less, based on the total amount of the lubricating oil composition, from the standpoint of the enhancement of the corrosion suppressing effect of copper.

The content of the component (B) is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, and further preferably 0.20% by mass or more, and is preferably 1.00% by mass or less, more preferably 0.70% by mass or less, and further preferably 0.50% by mass or less, based on the total amount of the lubricating oil composition, from the standpoint of the suppression of corrosion of copper and lead in a well-balanced manner.

The mass ratio ((A)/(B)) of the content of the component (A) and the component (B) is preferably 0.01 or more, more preferably 0.03 or more, and further preferably 0.05 or more, and is preferably 3.00 or less, more preferably 1.00 or less, and further preferably 0.60 or less, from the standpoint of the suppression of corrosion of copper and lead in a well-balanced manner.

As the component (B), the epoxy compounds may be used alone or may be used in combination of two or more kinds thereof. The preferred ranges of the total content in the case where two or more kinds of the components (B) are used in combination are the same as the preferred ranges in the case where the component (B) is used alone.

<Ashless Friction Modifier (C)>

The lubricating oil composition contains the ashless friction modifier (C) (which may be hereinafter referred simply to a “component (C)”) in an amount of 0.20% by mass or more based on the total amount of the lubricating oil composition.

When the content of the component (C) is less than 0.20% by mass based on the total amount of the lubricating oil composition, it is difficult to provide a lubricating oil composition excellent in friction reducing effect. The content of the component (C) is preferably 0.25% by mass or more, and more preferably 0.30% by mass or more, based on the total amount of the lubricating oil composition, from the standpoint of the achievement of a lubricating oil composition excellent in friction reducing effect.

The content of the component (C) is preferably 1.00% by mass or less, more preferably 0.70% by mass or less, and further preferably 0.60% by mass or less, based on the total amount of the lubricating oil composition, from the standpoint of the suppression of corrosion of copper and lead.

The content of the component (C) is preferably 0.25% by mass or more, and more preferably 0.30% by mass or more, and is preferably 1.00% by mass or less, and more preferably 0.70% by mass or less, based on the total amount of the lubricating oil composition, from the standpoint of the achievement of an excellent friction reducing effect and the suppression of corrosion of copper and lead.

Preferred examples of the component (C) include an ashless friction modifier containing at least one kind of an atom selected from the group consisting of a nitrogen atom and an oxygen atom in the molecule, and examples thereof include an ashless friction modifier, such as an amine compound, an aliphatic ester, an aliphatic amide, a fatty acid, an aliphatic alcohol, an aliphatic ether, a urea-based compound, and a hydrazide-based compound. Among these, more preferred examples thereof include an ashless friction modifier having at least one alkyl group or alkenyl group having a number of carbon atoms of 6 or more and 30 or less in the molecule thereof, such as an aliphatic ester, an aliphatic amide, a fatty acid, an aliphatic alcohol, an aliphatic amine, and an aliphatic ether.

Further preferred examples thereof include an ashless friction modifier having two or more hydroxy groups in the molecule of the component (C), and examples thereof include at least one selected from the group consisting of an ester compound having two or more hydroxy groups in the molecule of the component (C) (which may be hereinafter referred to as an “ester-based friction modifier”), an amine compound having two or more hydroxy groups in the molecule of the component (C) (which may be hereinafter referred to as an “amine-based friction modifier”), an amide compound having two or more hydroxy groups in the molecule of the component (C) (which may be hereinafter referred to as an “amide-based friction modifier”), and an ether compound having two or more hydroxy groups in the molecule of the component (C) (which may be hereinafter referred to as an “ether-based friction modifier”). Among these, an ester compound having two or more hydroxy groups in the molecule of the component (C) is preferred since the corrosion suppressing effect due to the component (A) and the component (B) can be readily obtained.

The number of hydroxy groups in the molecule of the component (C) is preferably 2 or more and 6 or less from the standpoint of the friction reducing effect and the solubility in the base oil.

Examples of the ester-based friction modifier include a partial ester compound, such as a partial ester compound obtained through reaction of a fatty acid and an aliphatic polyhydric alcohol.

The fatty acid is preferably a fatty acid having a linear-chain or branched hydrocarbon group having a number of carbon atoms of 6 or more and 32 or less, and the number of carbon atoms of the hydrocarbon group is more preferably 8 or more and 24 or less, and further preferably 16 or more and 20 or less, from the standpoint of the easiness in providing the friction reducing effect.

Examples of the linear-chain or branched hydrocarbon group having a number of carbon atoms of 6 or more and 32 or less include an alkyl group, such as a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an icosyl group, a pentacosyl group, a docosyl group, a tricosyl group, a tetracosyl group, a pentacosyl group, a hexacosyl group, a heptacosyl group, an octacosyl group, a nonacosyl group, and a triacontyl group; an alkenyl group, such as a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, a hexadecenyl group, a heptadecenyl group, a octadecenyl group, an oleyl group, a nonadecenyl group, an icosenyl group, a henicosenyl group, a docosenyl group, a tricosenyl group, a tetracosenyl group, a pentacosenyl group, a hexacosenyl group, a heptacosenyl group, an octacosenyl group, a nonacosenyl group, and a triacontenyl group; and a hydrocarbon group having two double bonds.

Examples of the fatty acid include a saturated fatty acid, such as caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, behenic acid, and lignoceric acid; and an unsaturated fatty acid, such as myristoleic acid, palmitoleic acid, oleic acid, and linolenic acid, and an unsaturated fatty acid is preferred from the standpoint of the friction reducing effect.

The aliphatic polyhydric alcohol may be a dihydric or higher hydric and hexahydric or lower hydric alcohol, examples of which include ethylene glycol, glycerin, trimethylolpropane, pentaerythritol, and sorbitol, and glycerin is preferred from the standpoint of the friction reducing effect.

Examples of a fatty acid partial ester compound obtained through reaction of glycerin and the unsaturated fatty acid (which may be hereinafter referred to as a “glycerin ester compound”) include a monoester, such as glycerin monomyristate, glycerin monopalmitate, glycerin monooleate; and a diester, such as glycerin dimyristate, glycerin dipalmitate, and glycerin dioleate, and a monoester is preferred. Examples of the partial ester compound also include a reaction product with a silicon compound or a boron compound.

More preferred examples of the monoester of the glycerin ester compound include an ester compound represented by the following general formula (II).

In the general formula (II), R²¹ represents a hydrocarbon group having a number of carbon atoms of 1 or more and 32 or less; and R²² to R²⁶ each independently represent a hydrogen atom or a hydrocarbon group having a number of carbon atoms of 1 or more and 18 or less.

The number of carbon atoms of the hydrocarbon group represented by R²¹ is preferably 8 or more and 32 or less, more preferably 12 or more and 24 or less, and further preferably 16 or more and 20 or less.

Examples of the hydrocarbon group represented by R²¹ include an alkyl group, an alkenyl group, an alkylaryl group, a cycloalkyl group, and a cycloalkenyl group, and among these, an alkyl group and an alkenyl group are preferred, and an alkenyl group is preferred.

Examples of the alkyl group represented by R²¹ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an icosyl group, a henicosyl group, a docosyl group, a tricosyl group, and a tetracosyl group, in which these groups may be any of linear-chain, branched, and cyclic.

Examples of the alkenyl group represented by R²¹ include a vinyl group, a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, a hexadecenyl group, a heptadecenyl group, an octadecenyl group, an oleyl group, a nonadecenyl group, an icosenyl group, a henicosenyl group, a docosenyl group, a tricosenyl group, and a tetracosenyl group, in which these groups may be any of linear-chain, branched, and cyclic, and the position of the double bond is arbitrary.

R²² to R²⁶ each independently preferably represent one selected from the group consisting of a hydrogen atom and a hydrocarbon group having a number of carbon atoms of 1 or more and 18 or less, and more preferably represent a hydrogen atom. It is preferred that all R²² to R²⁶ represent hydrogen atoms.

In the case where R²² to R²⁶ each is a hydrocarbon group, the hydrocarbon groups each may be saturated or unsaturated, aliphatic or aromatic, and linear-chain, branched, or cyclic. In the case where R²² to R²⁶ each is a hydrocarbon group, the numbers of carbon atoms of the hydrocarbon groups each independently preferably is a number of carbon atoms of 1 or more and 18 or less, more preferably a number of carbon atoms of 1 or more and 12 or less, further preferably a number of carbon atoms of 1 or more and 4 or less, and still further preferably a number of carbon atoms of 2.

Examples of the ester compound represented by the general formula (II) include a glycerin fatty acid monoester, such as glycerin 1-laurate, glycerin 1-stearate, glycerin 1-myristate, and glycerin 1-oleate, and among these, glycerin 1-oleate is preferred.

The ester-based friction modifier may be used alone or as a combination of two or more kinds thereof, and the ester compound represented by the general formula (II) may be used alone or as a combination of two or more kinds thereof.

Preferred examples of the amine-based friction modifier include an amine compound represented by the following general formula (III).

In the general formula (III), R³¹ represents a hydrocarbon group having a number of carbon atoms of 1 or more and 32 or less; R³² to R³⁹ each independently represent a hydrogen atom, a hydrocarbon group having a number of carbon atoms of 1 or more and 18 or less, or an oxygen-containing hydrocarbon group containing an ether bond or an ester bond; and a and b each independently represent an integer of 1 or more and 20 or less.

In the case where a is 2 or more, while there are plural units represented by each of R³² to R³⁵, the plural units represented by R³² may be the same or different, the plural units represented by R³³ may be the same or different, the plural units represented by R³⁴ may be the same or different, and the plural units represented by R³⁵ may be the same or different.

In the case where b is 2 or more, while there are plural units represented by each of R³⁶ to R³⁹, the plural units represented by R³⁶ may be the same or different, the plural units represented by R³⁷ may be the same or different, the plural units represented by R³⁸ may be the same or different, and the plural units represented by R³⁹ may be the same or different.

The number of carbon atoms of the hydrocarbon group represented by R³¹ is preferably 8 or more and 32 or less, more preferably 10 or more and 24 or less, and further preferably 12 or more and 20 or less.

Examples of the hydrocarbon group represented by R³¹ include an alkyl group, an alkenyl group, an alkylaryl group, a cycloalkyl group, and a cycloalkenyl group, and among these, an alkyl group and an alkenyl group are preferred.

Examples of the alkyl group represented by R³¹ include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an icosyl group, a henicosyl group, a docosyl group, a tricosyl group, and a tetracosyl group, in which these groups may be any of linear-chain, branched, and cyclic.

Examples of the alkenyl group represented by R³¹ include a vinyl group, a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, a hexadecenyl group, a heptadecenyl group, an octadecenyl group, an oleyl group, a nonadecenyl group, an icosenyl group, a henicosenyl group, a docosenyl group, a tricosenyl group, and a tetracosenyl group, in which these groups may be any of linear-chain, branched, and cyclic, and the position of the double bond is arbitrary.

The hydrocarbon groups represented by R³² to R³⁹ each may be saturated or unsaturated, aliphatic or aromatic, and linear-chain, branched, or cyclic, and examples thereof include an aliphatic hydrocarbon group, such as an alkyl group and an alkenyl group (in which the position of the double bond is arbitrary), or an aromatic hydrocarbon group. Examples of the hydrocarbon group include an aliphatic hydrocarbon group, such as a methyl group, an ethyl group, a propyl group, a butyl group, a butenyl group, a hexyl group, a hexenyl group, an octyl group, an octenyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, a decenyl group, a dodecyl group, a dodecenyl group, a tridecyl group, a tetradecyl group, a tetradecenyl group, a pentadecyl group, a hexadecyl group, a hexadecenyl group, a heptadecyl group, an octadecyl group, an octadecenyl group, a stearyl group, an isostearyl group, an oleyl group, a linoleic group, a cyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, an ethylcyclohexyl group, a propylcyclohexyl group, a dimethylcyclohexyl group, and trimethylcyclohexyl group; and an aromatic hydrocarbon group, such as a phenyl group, a methylphenyl group, an ethylphenyl group, a dimethylphenyl group, a propylphenyl group, a trimethylphenyl group, a butylphenyl group, and a naphthyl group.

In the case where R³² to R³⁹ each is a hydrocarbon group, the numbers of carbon atoms of the hydrocarbon groups each independently preferably is a number of carbon atoms of 1 or more and 18 or less, more preferably a number of carbon atoms of 1 or more and 12 or less, further preferably a number of carbon atoms of 1 or more and 4 or less, and still further preferably a number of carbon atoms of 2.

Examples of the oxygen-containing hydrocarbon group containing an ether bond or an ester bond include a group having a number of carbon atoms of 1 or more and 18 or less, and examples thereof include a methoxyethyl group, an ethoxymethyl group, a propoxymethyl group, an isopropoxymethyl group, a n-butoxymethyl group, a t-butoxymethyl group, a hexyloxymethyl group, an octyloxymethyl group, a 2-ethylhexyloxymethyl group, a decyloxymethyl group, a dodecyloxymethyl group, a 2-butyloctyloxymethyl group, a tetradecyloxymethyl group, a hexadecyloxymethyl group, a 2-hexyldodecyloxymethyl group, an allyloxymethyl group, a phenoxy group, a benzyloxy group, a methoxyethyl group, a methoxypropyl group, a 1,1-bismethoxypropyl group, a 1,2-bismethoxypropyl group, an ethoxypropyl group, a (2-methoxyethoxy)propyl group, a (1-methyl-2-methoxy)propyl group, an acetyloxymethyl group, a propanoyloxymethyl group, a butanoyloxymethyl group, a hexanoyloxymethyl group, an octanoyloxymethyl group, a 2-ethylhexanoyloxymethyl group, a decanoyloxymethyl group, a dodecanoyloxymethyl group, a 2-butyloctanoyloxymethyl group, a tetradecanoyloxymethyl group, a hexadecanoyloxymethyl group, a 2-hexyldodecanoyloxymethyl group, and a benzoyloxymethyl group.

R³² to R³⁹ each independently preferably represent one selected from the group consisting of a hydrogen atom and a hydrocarbon group having a number of carbon atoms of 1 or more and 18 or less, and more preferably represent a hydrogen atom. It is preferred that all R³² to R³⁹ represent hydrogen atoms from the standpoint of the friction reducing effect.

a and b each independently preferably represent an integer of 1 or more and 10 or less, more preferably 1 or more and 5 or less, further preferably 1 or more and 2 or less, and still further preferably 1.

The total of the integers represented by a and b is preferably 2 or more and 20 or less, more preferably 2 or more and 10 or less, further preferably 2 or more and 4 or less, and still further preferably 2, from the standpoint of the easiness in providing the friction reducing effect.

As the amine-based friction modifier, the amine compound represented by the general formula (III) may be used alone or as a combination of two or more kinds thereof.

Examples of the amine compound represented by the general formula (III) include an amine compound having two 2-hydroxyalkyl groups, examples of which include octyldiethanolamine, decyldiethanolamine, dodecyldiethanolamine, tetradecyldiethanolamine, hexadecyldiethanolamine, stearyldiethanolamine, oleyldiethanolamine, coconut oil diethanolamine, palm oil diethanolamine, canola oil diethanolamine, and beef tallow diethanolamine; and an amine compound having two polyalkylene oxide structures, such as polyoxyethylene octylamine, polyoxyethylene decylamine, polyoxyethylene dodecylamine, polyoxyethylene tetradecylamine, polyoxyethylene hexadecylamine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene beef tallow amine, polyoxyethylene coconut oil amine, polyoxyethylene palm oil amine, polyoxyethylene laurylamine, and ethylene oxide propylene oxide stearylamine. Among these, oleyldiethanolamine is preferred.

Preferred examples of the amide-based friction modifier include an amide compound represented by the following general formula (IV).

In the general formula (IV), R⁴¹ may be the same ones as described for R³¹ in the general formula (III), and the preferred embodiments thereof are also the same. In the general formula (IV), R⁴² to R⁴⁹ each independently may be the same ones as described for R³² to R³⁹ in the general formula (III), and the preferred embodiments thereof are also the same. In the general formula (IV), c and d each independently represent an integer of 1 or more and 20 or less.

c and d each independently preferably represent an integer of 1 or more and 10 or less, more preferably 1 or more and 5 or less, further preferably 1 or more and 2 or less, and still further preferably 1.

The total of the integers represented by c and d is preferably 2 or more and 20 or less, more preferably 2 or more and 10 or less, further preferably 2 or more and 4 or less, and still further preferably 2.

In the case where c is 2 or more, while there are plural units represented by each of R⁴² to R⁴⁵, the plural units represented by R⁴² may be the same or different, the plural units represented by R⁴³ may be the same or different, the plural units represented by R⁴⁴ may be the same or different, and the plural units represented by R⁴⁵ may be the same or different.

In the case where d is 2 or more, while there are plural units represented by each of R⁴⁶ to R⁴⁹, the plural units represented by R⁴⁶ may be the same or different, the plural units represented by R⁴⁷ may be the same or different, the plural units represented by R⁴⁸ may be the same or different, and the plural units represented by R⁴⁹ may be the same or different.

Examples of the amide compound represented by the general formula (IV) include an amide compound having two 2-hydroxyalkyl groups, examples of which include N,N-bis(2-hydroxyethyl)octanamide, N,N-bis(2-hydroxyethyl)decanamide, N,N-bis(2-hydroxyethyl)dodecanamide, N,N-bis(2-hydroxyethyl)tetradecanamide, N,N-bis(2-hydroxyethyl)hexadecanamide, N,N-bis(2-hydroxyethyl)octadecanamide (which is the same as N,N-bis(2-hydroxyethyl)stearic acid amide), N,N-bis(2-hydroxyethyl)oleamide (which is the same as oleic acid diethanolamide), coconut oil diethanolamide, palm oil diethanolamide, caster oil diethanolamide, and beef tallow diethanolamide; and an amide compound having two polyalkylene oxide structures, such as polyoxyethylene octylamide, polyoxyethylene decylamide, polyoxyethylene dodecylamide, polyoxyethylene tetradecylamide, polyoxyethylene hexadecylamide, polyoxyethylene stearylamide, polyoxyethylene oleylamide, polyoxyethylene beef tallow amide, polyoxyethylene coconut oil amide, polyoxyethylene palm oil amide, polyoxyethylene laurylamide, and ethylene oxide propylene oxide stearylamide. Among these, oleic acid diethanolamide is preferred.

As the amide-based friction modifier, the amide compound represented by the general formula (IV) may be used alone or as a combination of two or more kinds thereof.

Preferred examples of the ether-based friction modifier include a (poly)glycerin ether compound, and more preferred examples thereof include a (poly)glycerin ether compound represented by the following general formula (V). In the description herein, the (poly)glycerin ether compound means both a glycerin ether and a polyglycerin ether.

In the general formula (V), R⁵¹ represents a hydrocarbon group; and e represents an integer of 1 or more and 10 or less.

Examples of the hydrocarbon group represented by R⁵¹ include an alkyl group having a number of carbon atoms of 1 or more and 30 or less, an alkenyl group having a number of carbon atoms of 3 or more and 30 or less, an aryl group having a number of carbon atoms of 6 or more and 30 or less, and an aralkyl group having a number of carbon atoms of 7 or more and 30 or less.

The alkyl group having a number of carbon atoms of 1 or more and 30 or less represented by R⁵¹ may be any of linear-chain, branched-chain, and cyclic. Specific examples of the alkyl group include groups of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl, tridecyl, isotridecyl, tetradecyl, hexadecyl, octadecyl, icosyl, docosyl, tetracosyl, triacontyl, 2-octyldodecyl, 2-dodecylhexadecyl, 2-tetradecyloctadecyl, 16-methylheptadecyl, cyclopentyl, cyclohexyl, methylcyclohexyl, and cyclooctyl.

The alkenyl group having a number of carbon atoms of 3 or more and 30 or less represented by R⁵¹ may be any of linear-chain, branched-chain, and cyclic, and the position of the double bond is arbitrary. Specific examples of the alkenyl group include a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a pentenyl group, an isopentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tetradecenyl group, an octadecenyl group, an oleyl group, a cyclopentenyl group, a cyclohexenyl group, a methylcyclopentenyl group, and a methylcyclohexenyl group.

Examples of the aryl group having a number of carbon atoms of 6 or more and 30 or less represented by R⁵¹ include a phenyl group, a naphthyl group, a tolyl group, a xylyl group, a cumenyl group, a mesityl group, an ethylphenyl group, a propylphenyl group, a butylphenyl group, a pentylphenyl group, a hexylphenyl group, a heptylphenyl group, an octylphenyl group, and a nonylphenyl group.

Examples of the aralkyl group having a number of carbon atoms of 7 or more and 30 or less represented by R⁵¹ include a benzyl group, a phenethyl group, a naphthylmethyl group, a benzhydryl group, a trityl group, a methylbenzyl group, and a methylphenethyl group.

R⁵¹ is preferably an alkyl group or alkenyl group having a number of carbon atoms of 8 or more and 20 or less from the standpoint of the capability, the availability, and the like of the (poly)glycerin ether compound represented by the general formula (V).

e shows the polymerization degree of a (poly)glycerin as a raw material of the (poly)glycerin ether compound represented by the general formula (V), represents an integer of 1 or more and 10 or less, and preferably represents an integer of 1 or more and 3 or less from the standpoint of the achievement of the high friction reducing effect.

Examples of the (poly)glycerin ether compound represented by the general formula (V) include glycerin monododecyl ether, glycerin monotetradecyl ether, glycerin monohexadecyl ether (which is the same as chimyl alcohol), glycerin monooctadecyl ether (which is the same as batyl alcohol), glycerin monooleyl ether (which is the same as selachyl alcohol), diglycerin monododecyl ether, diglycerin monotetradecyl ether, diglycerin monohexadecyl ether, diglycerin monooctadecyl ether, diglycerin monooleyl ether, triglycerin monododecyl ether, triglycerin monotetradecyl ether, triglycerin monohexadecyl ether, triglycerin monooctadecyl ether, and triglycerin monooleyl ether.

As the ether-based friction modifier, the (poly)glycerin ether compound represented by the general formula (V) may be used alone or as a combination of two or more kinds thereof.

The component (C) may be used alone or as a combination of two or more kinds thereof, and a compound selected from the group consisting of the compounds represented by the general formulae (II) to (V) may be used alone or as a combination of two or more kinds thereof. The preferred ranges of the total content of the component (C) in the case where two or more kinds thereof are used in combination is the same as the preferred ranges thereof in the case where the component (C) is used alone.

<Additional Components>

The lubricating oil composition may appropriately contain additional additives, such as a viscosity index improver, a pour point depressant, a detergent dispersant, an antioxidant, a friction modifier other than the component (C) (which may be hereinafter referred simply to as an “additional friction modifier”) or an anti-wear agent, an extreme pressure agent, a rust inhibitor, a surfactant or a demulsifier, and an anti-foaming agent, in such a range that does not impair the object of the present invention, depending on necessity.

Examples of the viscosity index improver include a polymethacrylate (PMA)-based viscosity index improver (such as a polyalkyl methacrylate and a polyalkyl acrylate), an olefin copolymer (OCP)-based viscosity index improver (such as an ethylene-propylene copolymer (EPC) and a polybutylene), and a styrene-based copolymer (such as a polyalkylstyrene, a styrene-diene copolymer, a hydrogenated styrene-diene copolymer, a styrene-maleic anhydride copolymer, and a styrene-isobutylene copolymer). Examples of the PMA-based viscosity index improver include a dispersion type and a non-dispersion type. The dispersion type PMA-based viscosity index improver is a homopolymer of an alkyl methacrylate or an alkyl acrylate, and a non-dispersion type PMA-based viscosity index improver is a copolymer of an alkyl methacrylate or an alkyl acrylate and a polar monomer having dispersibility (such as diethylaminoethyl methacrylate). As similar to the PMA-based viscosity index improver, the OCP-based viscosity index improver includes a dispersion type. The weight average molecular weight of the viscosity index improver is preferably 5,000 or more and 1,500,000 or less, and for the PMA-based viscosity index improver, the weight average molecular weight thereof is preferably 20,000 or more, and more preferably 100,000 or more, and is preferably 1,000,000 or less, and more preferably 800,000 or less. For the OCP-based viscosity index improver, the weight average molecular weight thereof is preferably 10,000 or more, and more preferably 20,000 or more, and is preferably 800,000 or less, and more preferably 500,000 or less. For the styrene-based copolymer, the weight average molecular weight is preferably 10,000 or more, and more preferably 20,000 or more, and is preferably 800,000 or less, and more preferably 650,000 or less.

The viscosity index improver contains, for example, the aforementioned polymer, as a resin component, and in general, is often commercially available in the form of a solution containing the resin component containing the polymer diluted with a diluting oil, such as a mineral oil, in consideration of the handleability and the solubility in the aforementioned base oil. The concentration of the resin component of the viscosity index improver is generally 10% by mass or more and 50% by mass or less based on the total amount of the viscosity index improver.

The viscosity index improver may be used alone or as an arbitrary combination of two or more kinds thereof. The content of the viscosity index improver is preferably 0.01% by mass or more, more preferably 0.10% by mass or more, and further preferably 0.20% by mass or more, and is preferably 5.00% by mass or less, more preferably 2.00% by mass or less, and further preferably 1.00% by mass or less, in terms of content of the resin component, based on the total amount of the lubricating oil composition.

Examples of the pour point depressant include an ethylene-vinyl acetate copolymer, a condensate of chlorinated paraffin and naphthalene, a condensate of chlorinated paraffin and phenol, a polymethacrylate-based pour point depressant (such as a polyalkyl methacrylate and polyalkyl acrylate), a polyalkylstyrene, polyvinyl acetate, and polybutene, and the polymethacrylate-based pour point depressant (for example, a polymethacrylate having a weight average molecular weight (Mw) of 5,000 or more and 50,000 or less) is preferably used. The pour point depressant may be used alone or as an arbitrary combination of two or more kinds thereof. The content thereof preferably 0.01% by mass or more, and more preferably 0.05% by mass or more, and is preferably 5.0% by mass or less, and more preferably 1.0% by mass or less, based on the total amount of the lubricating oil composition.

The detergent dispersant used may be an ashless dispersant and/or a metal-based detergent.

The ashless dispersant used may be an arbitrary ashless dispersant used for a lubricating oil. Examples thereof include a monomeric succinimide compound represented by the following general formula (VI-i), a dimeric succinimide compound represented by the following general formula (VI-ii), polybutenylbenzylamine, polybutenylamine, and derivatives, such as boric acid-modified derivative, of these compounds. The ashless dispersant may be used alone or as an arbitrary combination of two or more kinds thereof.

In the general formula (VI-i) and the general formula (VI-ii), R⁶¹, R⁶³, and R⁶⁴ each independently represent an alkenyl group or alkyl group having a number average molecular weight (Mn) of 500 or more and 3,000 or less. The number average molecular weights of R⁶¹, R⁶³, and R⁶⁴ each independently is preferably 1,000 or more and 3,000 or less. R⁶², R⁶⁵, and R⁶⁶ each independently represent an alkylene group having a number of carbon atoms of 2 or more and 5 or less.

f represents an integer of 1 or more and 10 or less, and g represents an integer of 0, or 1 or more and 10 or less.

When the number average molecular weights of R⁶¹, R⁶³, and R⁶⁴ each are 500 or more, the solubility in the base oil may be enhanced, and the number average molecular weights thereof each are 3,000 or less, the detergency can be prevented from being deteriorated.

Examples of the alkenyl group represented by R⁶¹, R⁶³, and R⁶⁴ include a polybutenyl group, a polyisobutenyl group, and an ethylene-propylene copolymer, and examples of the alkyl group represented thereby include groups obtained through hydrogenation of these groups.

Preferred examples of the alkenyl group include a polybutenyl group and a polyisobutenyl group. The polybutenyl group may be obtained through polymerization of a mixture of 1-butene and isobutene, or isobutene having high purity. Preferred examples of the alkyl group include group obtained through hydrogenation of a polybutenyl group or group obtained through hydrogenation of a polyisobutenyl group.

In the general formula (VI-i), f preferably represents an integer of 2 or more and 5 or less, and more preferably 3 or more and 4 or less. When f is 1 or more, the detergency may be enhanced, and when f is 10 or less, the solubility in the base oil can be prevented from being deteriorated.

In the general formula (VI-ii), g preferably represents an integer of 1 or more and 4 or less, and more preferably 2 or more and 3 or less. The value of g within the range is preferred from the standpoint of the detergency and the solubility in the base oil.

The alkenyl- or alkylsuccinimide compound can be produced, for example, by reacting an alkenylsuccinic anhydride obtained through reaction of a polyolefin and maleic anhydride or an alkylsuccinic anhydride obtained through hydrogenation thereof, with a polyamine.

The monomeric succinimide compound and the dimeric succinimide compound can be produced, for example, by changing the ratio in the reaction of an alkenylsuccinic anhydride or an alkylsuccinic anhydride with a polyamine.

The olefin monomer used for forming the polyolefin is preferably one kind or a mixture of two or more kinds of an α-olefin having a number of carbon atoms of 2 or more and 8 or less, and more preferably a mixture of isobutene and butene-1.

Examples of the polyamine include a simple diamine, such as ethylenediamine, propylenediamine, butylenediamine, and pentylenediamine; a polyalkylenepolyamine, such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, di(methylethylene)triamine, dibutylenetriamine, tributylenetetramine, and pentapentylenehexamine; and a piperazine derivative, such as aminoethylpiperazine.

In addition to the alkenyl- or alkylsuccinimide compound, a boron derivative of the compound and/or a compound obtained through modification of the compound with an organic acid may be used. The boron derivative of the alkenyl- or alkylsuccinimide compound used can be produced by the ordinary method.

For example, the boron derivative may be obtained in such a manner that the polyolefin is reacted with maleic anhydride to provide an alkenylsuccinic anhydride, which is then imidized by further reacting with an intermediate obtained through reaction of the polyamine with a boron compound, such as boron oxide, a boron halide, boric acid, boric anhydride, a borate ester, and an ammonium salt of boric acid.

In the case where the boron derivative of the alkenyl- or alkylsuccinimide compound is used, the boron content of the boron derivative is not particularly limited, is preferably 0.05% by mass or more, and more preferably 0.10% by mass or more, and is preferably 5.0% by mass or less, and more preferably 0.3% by mass or less, in terms of boron.

The content of the succinimide compound in terms of nitrogen atom is preferably 200 ppm by mass or more, and more preferably 300 ppm by mass or more, and is preferably 4,000 ppm by mass or less, more preferably 3,000 ppm by mass or less, and further preferably 2,500 ppm by mass or less, based on the total amount of the lubricating oil composition. When the content thereof is 200 ppm by mass or more, the effect thereof may be exerted, and the content thereof is 4,000 ppm by mass or less, the effect corresponding to the addition thereof may be obtained.

The succinimide compound has corrosiveness to lead, and thus is not preferably added in an amount more than necessary, and for achieving the oxidation stability of the lubricating oil and the prevention of metal corrosion simultaneously, it is necessary to select the imide compound appropriately. From the standpoint of the suppression of the corrosiveness to lead, the succinimide compound is preferably a dimeric polybutenylsuccinimide compound containing a polybutenyl group having a number average molecular weight of 900 or more, which is preferably contained in an amount of 60% by mass or more, and more preferably 70% by mass or more, based on the total nitrogen amount of the succinimide compound.

The succinimide compound may be used alone or as a combination of two or more kinds thereof.

As the metal-based detergent, an arbitrary alkaline earth metal-based detergent that is used for a lubricating oil may be used, and examples thereof include one or more kinds thereof selected from the group consisting of an alkaline earth metal sulfonate, an alkaline earth metal phenate, and an alkaline earth metal salicylate.

Examples of the alkaline earth metal sulfonate include an alkaline earth metal salt of an alkylaromatic sulfonic acid obtained through sulfonation of an alkylaromatic compound, preferred examples thereof include a magnesium salt and/or a calcium salt thereof, and more preferred examples thereof include a calcium salt thereof.

Preferred examples of the alkaline earth metal phenate include an alkaline earth metal salt of an alkylphenol, an alkylphenol sulfide, or a Mannich reaction product of an alkylphenol, more preferred examples thereof include a magnesium salt and/or a calcium salt thereof, and further preferred examples thereof include a calcium salt thereof.

Preferred examples of the alkaline earth metal salicylate include an alkaline earth metal salt of an alkylsalicylic acid, more preferred examples thereof include a magnesium salt and/or a calcium salt thereof, and further preferred examples thereof include a calcium salt thereof.

The alkyl group constituting the alkaline earth metal-based detergent is preferably an alkyl group having a number of carbon atoms of 4 or more and 30 or less, and more preferably an alkyl group having a number of carbon atoms of 6 or more and 18 or less, and the alkyl group may be linear-chain or branched. The alkyl group may be a primary alkyl group, a secondary alkyl group, or a tertiary alkyl group.

The alkaline earth metal sulfonate, the alkaline earth metal phenate, and the alkaline earth metal salicylate encompasses: not only a neutral alkaline earth metal sulfonate, a neutral alkaline earth metal phenate, and a neutral alkaline earth metal salicylate, which are obtained, for example, in such a manner that the alkylaromatic sulfonic acid, the alkylphenol, the alkylphenol sulfide, the Mannich reaction product of an alkylphenol, the alkylsalicylic acid, and the like described above are reacted directly with an alkaline earth metal base, such as an oxide and a hydroxide of an alkaline earth metal, e.g., magnesium and/or calcium, or are once converted to an alkali metal salt, such as a sodium salt and a potassium salt, which is then substituted with an alkaline earth metal salt; but also a basic alkaline earth metal sulfonate, a basic alkaline earth metal phenate, and a basic alkaline earth metal salicylate, which are obtained in such a manner that the neutral alkaline earth metal sulfonate, the neutral alkaline earth metal phenate, and the neutral alkaline earth metal salicylate are heated with an excess amount of an alkaline earth metal salt or an alkaline earth metal base in the presence of water; and a overbasic alkaline earth metal sulfonate, a overbasic alkaline earth metal phenate, and a overbasic alkaline earth metal salicylate, which are obtained in such a manner that the neutral alkaline earth metal sulfonate, the neutral alkaline earth metal phenate, and the neutral alkaline earth metal salicylate are reacted with a carbonate salt or a borate salt of an alkaline earth metal in the presence of carbon dioxide gas.

The metal-based detergent used in the present invention may be one or more selected from the group consisting of the neutral salts, the basic salts, and the overbasic salts described above, and a mixture of one or more selected from the overbasic salicylate, the overbasic phenate, and the overbasic sulfonate, with the neutral sulfonate is preferred from the standpoint of the detergency and the wear resistance.

The metal-based detergent is generally placed on the market in the form diluted with a light lubricant base oil or the like and commercially available, and the metal content thereof is, for example, 1.0% by mass or more and 20% by mass or less, and preferably 2.0% by mass or more and 16% by mass or less.

The base number of the metal-based detergent used in the present invention is preferably 10 mgKOH/g or more, and more preferably 15 mgKOH/g or more, and is preferably 500 mgKOH/g or less, and more preferably 450 mgKOH/g or less. The metal-based detergent selected from these materials may be used alone or as a combination of two or more kinds thereof. The base number referred herein means a base number by the potentiometric titration method (base number-perchloric acid method) measured according to JIS K2501, Petroleum products and lubricants, Determination of neutralization number.

The metal-based detergent may be contained alone or as an arbitrary combination of two or more kinds thereof. The content thereof is preferably 0.01% by mass or more, more preferably 0.5% by mass or more, and further preferably 1.0% by mass or more, and is preferably 10% by mass or less, more preferably 5.0% by mass or less, and further preferably 3.0% by mass or less, based on the total amount of the lubricating oil composition.

Examples of the antioxidant include a phenol-based antioxidant, an amine-based antioxidant, and a molybdenum amine complex-based antioxidant.

Examples of the phenol-based antioxidant include 4,4′-methylenebis(2,6-di-tert-butylphenol); 4,4′-bis(2,6-di-tert-butylphenol); 4,4′-bis(2-methyl-6-tert-butylphenol); 2,2′-methylenebis(4-ethyl-6-tert-butylphenol); 2,2′-methylenebis(4-methyl-6-tert-butylphenol); 4,4′-butylidenebis(3-methyl-6-tert-butylphenol); 4,4′-isopropylidenebis(2,6-di-tert-butylphenol); 2,2′-methylenebis(4-methyl-6-nonylphenol); 2,2′-isobutylidenebis(4,6-dimethylphenol); 2,2′-methylenebis(4-methyl-6-cyclohexylphenol); 2,6-di-tert-butyl-4-methylphenol; 2,6-di-tert -butyl-4-ethylphenol; 2,4-dimethyl-6-tert -butylphenol; 2,6-di-tert-amyl-p -cresol; 2,6-di-tert-butyl-4-(N,N′-dimethylaminomethylphenol); 4,4′-thiobis(2-methyl-6-tert-butylphenol); 4,4′-thiobis(3-methyl-6-tert-butylphenol); 2,2′-thiobis(4-methyl-6-tert-butylphenol); bis(3-methyl-4-hydroxy-5-tert-butylbenzyl) sulfide; bis(3,5-di-tert-butyl-4-hydroxybenzyl) sulfide; n-octyl-3-(4-hydroxy-3,5-di-tert-butylphenyl) propionate; n-octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate; 2,2′-thio[diethyl-bis-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]; and a benzenepropanoic acid, 3,5-bis(1,1-dimethyl-ethyl)-4-hydroxy-C7-C9 branched alkyl esters. Among these, the phenol-based antioxidant of the bisphenol-based antioxidant and the ester group-containing phenol-based antioxidant are preferred.

The phenol-based antioxidant may be contained alone or as an arbitrary combination of two or more kinds thereof. The content thereof is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.10% by mass or more, and is preferably 10% by mass or less, more preferably 5.0% by mass or less, and further preferably 3.0% by mass or less, based on the total amount of the lubricating oil composition.

Examples of the amine-based antioxidant include a monoalkyldiphenylamine-based antioxidant, such as monooctyldiphenylamine and monononyldiphenylamine; a dialkyldiphenylamine-based antioxidant, such as 4,4′-dibutyldiphenylamine, 4,4′-dipentyldiphenylamine, 4,4′-dihexyldiphenylamine, 4,4′-diheptyldiphenylamine, 4,4′-diocyldiphenylamine, and 4,4′-dinonyldiphenylamine; a polyalkyldiphenylamine-based antioxidant, such as tetrabutyldiphenylamine, tetrahexyldiphenylamine, tetraocyldiphenylamine, and tetranonyldiphenylamine; a phenylenediamine-based antioxidant, such as N,N′-diisopropyl-p-phenylenediamine, N,N′-diphenyl-p-phenylenediamine, and N-cyclohexyl-N′-phenyl-p-phenylenediamine; and a naphthylamine-based antioxidant, such as α-naphthylamine, phenyl-α-naphthylamine, and an alkyl-substituted phenyl-α-naphthylamine, e.g., butylphenyl-α-naphthylamine, pentylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine, heptylphenyl-α-naphthylamine, octylphenyl-α-naphthylamine, and nonylphenyl-α-naphthylamine. Among these, the amine-based antioxidant of the dialkyldiphenylamine-based antioxidant and the naphthylamine-based antioxidant are preferred.

The amine-based antioxidant may be contained alone or as an arbitrary combination of two or more kinds thereof. The content thereof is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.10% by mass or more, and is preferably 10% by mass or less, more preferably 5.0% by mass or less, and further preferably 3.0% by mass or less, based on the total amount of the lubricating oil composition.

The molybdenum amine complex-based antioxidant used may be a hexavalent molybdenum compound, specifically a compound obtained through reaction of molybdenum trioxide and/or molybdic acid with an amine compound, such as a compound obtained by the production method described in JP 2003-252887 A.

The amine compound to be reacted with a hexavalent molybdenum compound is not particularly limited, and examples thereof include a monoamine, a diamine, a polyamine, and an alkanolamine. Specific examples thereof include an alkylamine having an alkyl group having a number of carbon atoms of 1 or more and 30 or less (in which the alkyl group may be linear-chain or branched), such as methylamine, ethylamine, dimethylamine, diethylamine, methylethylamine, and methylpropylamine; an alkenylamine having an alkenyl group having a number of carbon atoms of 2 or more and 30 or less (in which the alkenyl group may be linear-chain or branched), such as ethenylamine, propenylamine, butenylamine, octenylamine, and oleylamine; an alkanolamine having an alkanol group having a number of carbon atoms of 1 or more and 30 or less (in which the alkanol group may be linear-chain or branched), such as methanolamine, ethanolamine, methanolethanolamine, and methanolpropanolamine; an alkylenediamine having an alkylene group having a number of carbon atoms of 1 or more and 30 or less, such as methylenediamine, ethylenediamine, propylenediamine, and butylenediamine; a polyamine, such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine; a compound obtained by substituting an alkyl group or alkenyl group having a number of carbon atoms of 8 or more and 20 or less on the monoamine, the diamine, or the polyamine described above, such as undecyldiethylamine, undecyldiethanolamine, dodecyldipropanolamine, oleyldiethanolamine, oleylpropylenediamine, and stearyltetraethylenepentamine; a heterocyclic compound, such as imidazoline; an alkylene oxide adduct of the these compounds; and a mixtures thereof. Examples thereof further include a sulfur-containing molybdenum complex of succinimide described in JPH3-22438 B and JP 2004-2866 A.

The antioxidant may be contained alone or as an arbitrary combination of two or more kinds thereof, and the phenol-based antioxidant and/or the amine-based antioxidant are preferably used.

The total content of the antioxidant is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.10% by mass or more, and is preferably 10% by mass or less, more preferably 5.0% by mass or less, and further preferably 3.0% by mass or less, based on the total amount of the lubricating oil composition.

Specific examples of the additional friction modifier and the anti-wear agent include a sulfur-based compound, such as an olefin sulfide, a dialkyl polysulfide, a diarylalkyl polysulfide, and diaryl polysulfide; a phosphorus-based compound, such as a phosphate ester, a thiophosphate ester, a phosphite ester, an alkyl hydrogen phosphite, a phosphate ester amine salt, and a phosphite ester amine salt; and an organic metal-based compound, such as zinc dialkyldithiophosphate (ZnDTP), zinc dithiocarbamate (ZnDTC), molybdenum oxysulfide organophosphorodithioate (MoDTP), and molybdenum oxysulfide dithiocarbamate (MoDTC). The friction modifier and the anti-wear agent may be contained alone or as an arbitrary combination of two or more kinds thereof.

The additional friction modifier and the anti-wear agent are preferably used in such a manner that the metal content and the sulfur content in the lubricating oil composition are decreased as much as possible, and the content thereof is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and further preferably 1.5% by mass or less, based on the total amount of the lubricating oil composition. In the case where the additional friction modifier and the anti-wear agent are used, the content thereof is preferably 0.01% by mass or more based on the total amount of the lubricating oil composition.

From the standpoint of the suppression of the corrosiveness to copper, the content in terms of molybdenum atom of the sulfur containing compound, such as molybdenum oxysulfide dithiocarbamate (MoDTC), as the additional friction modifier is preferably less than 0.02% by mass, and more preferably 0.01% by mass or less, based on the total amount of the lubricating oil composition, and it is further preferred that the compound is not contained.

Examples of the extreme pressure agent include a sulfur-based compound, such as an olefin sulfide, a dialkyl polysulfide, a diarylalkyl polysulfide, and diaryl polysulfide; and a phosphorus-based compound, such as a phosphate ester, a thiophosphate ester, a phosphite ester, an alkyl hydrogen phosphite, a phosphate ester amine salt, and a phosphite ester amine salt. The extreme pressure agent may be contained alone or as an arbitrary combination of two or more kinds thereof.

In the case where the extreme pressure agent is used, the content of the extreme pressure agent is preferably 0.01% by mass or more and 10% by mass or less based on the total amount of the lubricating oil composition.

Examples of the rust inhibitor include a petroleum sulfonate, an alkylbenzene sulfonate, dinonylnaphthalene sulfonate, an alkenyl succinate ester, and a polyhydric alcohol ester. The rust inhibitor may be contained alone or as an arbitrary combination of two or more kinds thereof. The content of the rust inhibitor is preferably 0.01% by mass or more and 1.00% by mass or less, and more preferably 0.05% by mass or more and 0.50% by mass or less, based on the total amount of the lubricating oil composition, from the standpoint of the effect thereof contained.

Examples of the surfactant or the demulsifier include a polyalkylene glycol-based nonionic surfactant, such as a polyoxyethylene alkyl ether, a polyoxyethylene alkylphenyl ether, and a polyoxyethylene alkylnaphthyl ether. The surfactant or the demulsifier may be contained alone or as an arbitrary combination of two or more kinds thereof.

Examples of the anti-foaming agent include a silicone oil, such as dimethylpolysiloxane, a fluorosilicone oil, and a fluoroalkyl ether. The anti-foaming agent may be contained alone or as an arbitrary combination of two or more kinds thereof. The content of the anti-foaming agent is preferably 0.001% by mass or more, and more preferably 0.005% by mass or more, and is preferably 0.150% by mass or less, and more preferably 0.100% by mass or less, based on the total amount of the lubricating oil composition, from the standpoint of the balance between the anti-foaming effect and the economical efficiency, and the like.

[Production Method of Lubricating Oil Composition for Internal Combustion Engine]

A production method of a lubricating oil composition as one embodiment of the present invention includes blending a base oil with (A) a benzotriazole derivative represented by the general formula (I):

wherein in the general formula (I), R¹ represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 9 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom; and R² represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 16 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom, (B) an epoxy compound, and (C) an ashless friction modifier, so as to make a content of the ashless friction modifier (C) of 0.20% by mass or more based on the total amount of the lubricating oil composition.

In a production method of a lubricating oil composition for an internal combustion engine as one embodiment of the present invention, an additional component other than the components (A) to (C) may further blended.

The base oil, the components (A) to (C), and the additional component are the same as those described for the lubricating oil composition above respectively, a lubricating oil composition that is produced by the production method is also the same as described above, and thus the descriptions thereof are omitted herein.

In the production method, the components (A) to (C) and the additional component may be blended with the base oil in any method, and the blending method is not limited.

[Lubricating Method Using Lubricating Oil Composition]

Examples of the lubricating method including using a lubricating oil composition as one embodiment of the present invention include a method of charging the lubricating oil composition as one embodiment of the present invention in an internal combustion engine, such as an engine, and lubricating among members of the internal combustion engine. More preferred examples thereof include a method of charging the lubricating oil composition in an internal combustion engine including members containing copper and/or lead, and lubricating among the members of the internal combustion engine.

[Applications of Lubricating Oil Composition]

The lubricating oil composition as one embodiment of the present invention can be favorably used as a lubricating oil for an internal combustion engine, such as a gasoline engine, a diesel engine, and a gas engine, for an automobile, such as a two-wheel vehicle and a four-wheel vehicle, an electric generator, a marine vessel, and the like. The lubricating oil composition can be more favorably used as a lubricating oil for lubricating an internal combustion engine including members containing copper and/or lead.

The lubricating oil composition as one embodiment of the present invention has an excellent friction reducing effect irrespective of the use of an ashless friction modifier as a friction modifier, and therefore is favorable for an application that requires reduction of a metal-based friction modifier, such as MoDTC, for example, as a lubricating oil composition for an internal combustion engine under severe environmental regulation, such as a gasoline engine, a diesel engine, an engine using dimethyl ether as a fuel, and a gas engine.

For example, the API Standard and the JASO Standard, which are the official standards of a diesel engine oil, include “Cummins Corrosion Test (ASTM D6594)”, and for satisfying the standards, it is necessary to suppress the elution amounts of copper and lead to certain values or less.

The lubricating oil composition as one embodiment of the present invention can be favorably used for lubricating among members of the internal combustion engine by charging in the internal combustion engine.

EXAMPLES

The present invention will be described with reference to examples, but the present invention is not limited to the examples.

In the description herein, the measurements of the properties of the raw materials used in Examples and Comparative Examples were performed according to the procedures shown below.

-   (1) Kinetic Viscosity

The kinetic viscosity was a value measured according to JIS K2283 using by a glass capillary viscometer.

-   (2) Viscosity Index

The viscosity index was a value measured according to JIS K2283.

-   (3) NOACK Value

The NOACK value was a value measured according to the method defined in ASTM D5800 (250° C., 1 hour).

-   (4) Ring Analysis (% C_(A) and % C_(P))

The ratio (percentage) of an aromatic component and the ratio (percentage) of a paraffin component calculated by the ring analysis n-d-M method shown by % C_(A) and % C_(P) respectively were measured according to ASTM D3238.

-   (5) Sulfur Content

The sulfur content was a value measured according to JIS K2541-6.

-   (6) Contents of Zinc Atoms, Calcium Atoms, Boron Atoms, and     Phosphorus Atoms

The contents of the atoms were values measured according to JPI -5S-38-2003.

-   (7) Content of Nitrogen Atoms

The content of nitrogen atoms was a value measured according to JIS K2609.

-   (8) Base Number

The base number was a value measured by the potentiometric titration method (base number-perchloric acid method) according to JIS K2501:2003.

-   (9) Weight Average Molecular Weight (Mw) of Styrene-Isobutylene     Copolymer

The weight average molecular weight (Mw) was a value measured under the following condition and calculated with the polystyrene calibration curve, and specifically measured under the following condition.

Equipment: “GPC-900” (a product name, produced by JASCO Corporation)

Columns: “TSK gel GMH6” (a product name, produced by Tosoh Corporation)×2

Solvent: THF

Temperature: 40° C.

Sample concentration: 0.5% by mass

Calibration curve: polystyrene

Detector: differential refractometer detector

The evaluation methods for the lubricating oil compositions of Example and Comparative Examples were as follows.

[Friction Reducing Effect]

With “High Frequency Friction Machine TE77” (produced by Phoenix Tribology, Ltd.), a preconditioning operation was performed with a test plate (material: SUJ-2, shape: 58 mm in length×37 mm in width×4 mm in thickness) and a test cylinder pin (material: SUJ-2, shape: 15 mm in diameter×22 mm in length) under conditions of an amplitude of 8 mm, a frequency of 10 Hz, an oil temperature of 80° C., and a load range of 50 N, for 10 minutes.

Thereafter, the friction coefficient was measured under conditions of an amplitude of 8 mm, a frequency of 10 Hz, an oil temperature of 80° C., a load of 100 N, and an operation time of 30 minutes, so as to evaluate the friction reducing effect.

[Corrosion Test]

100 mL of a lubricating oil composition was placed in a glass test tube (40 mm in diameter×300 mm in length), and a copper plate (25 mm×25 mm×1 mm) and a lead plate (25 mm×25 mm×1 mm) were polished and immersed in the test oil, and the corrosion test was performed. The test was performed at an oil temperature of 135° C. for 168 hours under blowing the air at a flow rate of 5 L/h. The result was evaluated by the elution amount of copper and the elution amount of lead. The elution amounts of copper and lead were measured according to JPI -5S-38-2003.

Examples 1 to 9 and Comparative Examples 1 to 11

Lubricating oil compositions of Examples and Comparative Examples containing the base oil and the components shown in Tables 2 and 3 were prepared by blending the base oil and the components according to the formulations shown in Tables 2 and 3. The lubricating oil compositions of Examples and Comparative Examples were evaluated according to the aforementioned evaluation methods. The results obtained are shown in Tables 2 and 3.

The components shown in Tables 1 to 3 below are as follows.

<Base Oil>

Base oil: hydrorefined base oil, 40° C. kinetic viscosity: 21 mm²/s, 100° C. kinetic viscosity: 4.5 mm²/s, viscosity index: 135, sulfur content: 1 ppm by mass, NOACK value: 12.6% by mass, n-d-M ring analysis: % C_(A): 0.0, % C_(P): 78.7

<Component (A), Benzotriazole Derivative Represented by General Formula (I)>

Copper deactivator 1: (4 or 5)-methylbenzotriazole (benzotriazole derivative represented by the general formula (I), in which R¹ is a methyl group, and R² is a hydrogen atom)

Copper deactivator 2: 1,2,3-benzotriazole (benzotriazole derivative represented by the general formula (I), in which R¹ and R² are hydrogen atoms)

<Component (B), Epoxy Compound>

Lead deactivator 1: 3,4-epoxycyclohexylmethyl (3,4-epoxy)cyclohexanecarboxylate

Lead deactivator 2: 1,2-epoxyhexadecane

<Component (C), Ashless Friction Modifier>

Ester-based friction modifier: glycerin monooleate (which is the same as glycerin 1-oleate)

Amine-based friction modifier: oleyldiethanolamine

Amide-based friction modifier: oleic acid diethanolamide

Ether-based friction modifier: “KIKU-LUBE (a trade name) FM-618C” (produced by ADEKA Corporation, oleyl polyglycelyl ether)

<Additional Component>

Copper deactivator 3: “IRGAMET (a trade name) 39” (produced by BASF AG, 1-(N,N-bis(2-ethylhexyl)aminomethyl)methylbenzotriazole, benzotriazole derivative represented by the general formula (I), in which R¹ is a methyl group, and R² is a hydrocarbyl group having a number of carbon atoms of 17 containing a nitrogen atom)

<Additional Additives>

Viscosity index improver: styrene-isobutylene copolymer, weight average molecular weight (Mw): 580,000, resin amount: 10% by mass

Pour point depressant: polymethacrylate

Metal-based detergent 1: calcium sulfonate, base number (perchloric acid method): 17 mgKOH/g, calcium content: 2.4% by mass

Metal-based detergent 2: calcium salicylate, base number (perchloric acid method): 225 mgKOH/g, calcium content: 7.8% by mass

Metal-based detergent 3: calcium salicylate, base number (perchloric acid method): 350 mgKOH/g, calcium content: 12.5% by mass

Anti-wear agent: zinc dialkyldithiophosphate, zinc content: 9.0% by mass, phosphorus content: 8.2% by mass, sulfur content: 17.1% by mass

Phenol-based antioxidant: octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate

Amine-based antioxidant: dialkyldiphenylamine, nitrogen content: 4.6% by mass

Ashless dispersant 1: polybutenylsuccinimide, nitrogen content: 1.0% by mass

Ashless dispersant 2: boron derivative of polybutenylsuccinimide, nitrogen content: 1.2% by mass, boron content: 1.3% by mass

Anti-foaming agent: dimethylpolysiloxane

The blending amounts of the additional additives are shown in Table 1.

TABLE 1 Blended amount Component (% by mass) *1 Viscosity index improver 7.00 Pour point depressant 0.20 Metal-based detergent 1 0.65 Metal-based detergent 2 1.00 Metal-based detergent 3 0.80 Anti-wear agent 1.10 Phenol-based antioxidant 0.50 Amine-based antioxidant 0.90 Ashless dispersant 1 5.00 Ashless dispersant 2 1.00 Anti-foaming agent 0.10 Total 18.25 *1: blending amount based on the total amount of the lubricating oil composition

TABLE 2 Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Unit ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 ple 7 ple 8 ple 9 Formulation Base oil — bal- bal- bal- bal- bal- bal- bal- bal- bal- ance ance ance ance ance ance ance ance ance Component Copper deactivator 1 % by 0.05 0.05 0.02 0.05 0.10 0.05 0.05 0.05 — (A) mass Copper deactivator 2 % by — — — — — — — — 0.05 mass Component Lead deactivator 1 % by 0.30 0.50 0.30 0.30 0.30 — 0.10 0.30 0.30 (B) mass Lead deactivator 2 % by — — — — — 0.30 — — — mass Component Ester-based friction % by 0.30 0.60 — — — 0.60 0.60 0.60 0.60 (C) modifier mass Amine-based friction % by — — 0.60 — — — — — — modifier mass Amide-based friction % by — — — 0.60 — — — — — modifier mass Ether-based friction % by — — — — 0.60 — — — — modifier mass Copper deactivator 3 % by — — — — — — — — — mass Additional additives % by 18.25 18.25 18.25 18.25  18.25 18.25 18.25 18.25 18.25 mass Total % by 100.00 100.00 100.00 100.00  100.00 100.00 100.00 100.00 100.00 mass Properties of Corrosion Copper (Cu) eluted ppm by 12 9 17 16    7 18 10 15 12 composition test amount mass Lead (Pb) eluted ppm by 18 23 24 less 30 38 44 27 30 amount mass than 10 Friction test Friction coefficient — 0.117 0.115 0.105  0.112 0.115 0.114 0.114 0.115 0.117

TABLE 3 Comparative Comparative Comparative Comparative Comparative Comparative Unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Formulation Base oil — balance balance balance balance balance balance Component Copper % by — — — — — — (A) deactivator 1 mass Copper % by — — — — — — deactivator 2 mass Component Lead % by 0.30 0.30 0.30 0.30 0.30 — (B) deactivator 1 mass Lead % by — — — — — — deactivator 2 mass Component Ester-based % by 0.30 — — — 0.30 0.30 (C) friction modifier mass Amine-based % by — 0.30 — — — — friction modifier mass Amide-based % by — — 0.30 — — — friction modifier mass Ether-based % by — — — 0.30 — — friction modifier mass Copper deactivator 3 % by 0.05 0.05 0.05 0.05 — 0.05 mass Additional additives % by 18.25 18.25 18.25 18.25 18.25 18.25 mass Total % by 100.00 100.00 100.00 100.00 100.00 100.00 mass Properties of Corrosion Copper (Cu) ppm by 100 73 63 104 80 17 composition test eluted amount mass Lead (Pb) ppm by 40 21 32 21 33 174 eluted amount mass Friction test Friction — 0.117 0.108 0.115 0.117 0.116 0.118 coefficient Comparative Comparative Comparative Comparative Comparative Unit Example 7 Example 8 Example 9 Example 10 Example 11 Formulation Base oil — balance balance balance balance balance Component Copper % by — — — — — (A) deactivator 1 mass Copper % by — — — — — deactivator 2 mass Component Lead % by — — — — — (B) deactivator 1 mass Lead % by — — — — — deactivator 2 mass Component Ester-based % by — — — 0.10 — (C) friction modifier mass Amine-based % by 0.30 — — — — friction modifier mass Amide-based % by — 0.30 — — — friction modifier mass Ether-based % by — — 0.30 — — friction modifier mass Copper deactivator 3 % by 0.05 0.05 0.05 — — mass Additional additives % by 18.25 18.25 18.25 18.25 18.25 mass Total % by 100.00 100.00 100.00 100.00 100.00 mass Properties of Corrosion Copper (Cu) ppm by 32 28 25 35 18 composition test eluted amount mass Lead (Pb) ppm by 112 103 108 72 52 eluted amount mass Friction test Friction — 0.109 0.119 0.120 0.129 0.132 coefficient

It was apparent from the results in Tables 2 and 3 that the lubricating oil compositions of Examples 1 to 9 were confirmed to be excellent in friction reducing effect and excellent in corrosion suppressing effects of members containing copper and lead.

On the other hand, the lubricating oil compositions of Comparative Examples 1 to 11 were confirmed to fail to provide good corrosion suppressing effects of members containing copper and lead.

Specifically, the following matters were confirmed. The values of the contents of the additives in the following description each are a content based on the total amount of the lubricating oil composition.

The lubricating oil composition of Comparative Example 11 did not contain the components (A) to (C) but contained only the base oil and the additional additives, and it was found that in this case, a sufficient friction reducing effect did not obtained, and the composition was not favorable as a lubricating oil composition.

The lubricating oil composition of Comparative Example 10 contained 0.10% by mass of the component (C) in addition to the base oil and the additional additives, but a sufficient friction reducing effect did not obtained since the content of the component (C) was as small as 0.10% by mass. Furthermore, due to the component (C) contained, such a result was obtained that corrosion of copper and lead further proceeded, as compared to the lubricating oil composition of Comparative Example 11 irrespective of the small content of the component (C).

The lubricating oil compositions of Comparative Examples 6 to 9 contained 0.30% by mass of the components (C) different from each other in addition to the base oil and the additional additives, and further contained 0.05% by mass of the copper deactivator 3. In Comparative Examples 6 to 9, such a result was obtained that a friction reducing effect was exhibited due to the large content of the component (C) of 0.30% by mass, but corrosion of lead proceeded since the component (A) and the component (B) were not contained.

The lubricating oil composition of Comparative Example 5 contained 0.30% by mass of the lead deactivator 1 as the component (B) instead of the copper deactivator 3 in the lubricating oil composition of Comparative Example 6, and in this case, such a result was obtained that corrosion of lead was suppressed, but corrosion of copper proceeded.

The lubricating oil composition of Comparative Example 1 contained 0.05% by mass of the copper deactivator 3 and 0.30% by mass of the lead deactivator 1 as the component (B) for achieving the corrosion suppressing effects of copper and lead simultaneously. However, such a result was surprisingly obtained that corrosion of copper significantly proceeded with the lubricating oil composition of Comparative Example 1.

Similarly, the lubricating oil compositions of Comparative Examples 2 to 4, in which the kind of the component (C) used in Comparative Example 1 was changed, provided such a result that corrosion of copper was not sufficiently suppressed as similar to Comparative Example 1.

On the other hand, the lubricating oil compositions of Examples 1 to 9 of the present invention contained the ashless friction modifier as the component (C) in a large amount, and thus provided an excellent friction reducing effect. Furthermore, it was confirmed that irrespective of the large content of the component (C), an excellent corrosion suppressing effects of members containing copper and lead due to the component (A) and the component (B) contained.

Furthermore, it was surprisingly confirmed that the lubricating oil compositions of Examples 1 to 9 of the present invention had an excellent corrosion suppressing effects of copper and lead, even as compared to the lubricating oil composition of Comparative Example 11 not containing the components (A) to (C). Accordingly, it was confirmed that not only the aforementioned disadvantage caused by the combination use of the copper deactivator and the lead deactivator was avoided, but also such a lubricating oil composition was provided that was excellent in friction reducing effect and also excellent in corrosion suppressing effects of members containing copper and lead, due to the synergistic effect of the combination of the component (A) and the component (B), irrespective of the ashless friction modifier used in the lubricating oil composition.

INDUSTRIAL APPLICABILITY

The lubricating oil composition of the present invention is a lubricating oil composition using an ashless friction modifier, and is excellent in friction reducing effect and also excellent in corrosion suppressing effects of copper and lead. Accordingly the lubricating oil composition is favorable as a lubricating oil composition for members containing copper and lead, and is more favorable as a lubricating oil composition for an internal combustion engine using the members. Furthermore, the lubricating oil composition has an excellent friction reducing effect irrespective of the use of an ashless friction modifier as a friction modifier, and therefore is favorable for an application that requires reduction of a metal-based friction modifier, such as MoDTC, for example, as a lubricating oil composition for an internal combustion engine under severe environmental regulation, such as a gasoline engine, a diesel engine, an engine using dimethyl ether as a fuel, and a gas engine. 

1. A lubricating oil composition, comprising: a base oil; (A) a benzotriazole derivative of formula (I):

wherein: R¹ represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 9 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom; and R² represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 16 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom, (B) an epoxy compound; and (C) an ashless friction modifier, wherein the ashless friction modifier (C) is present in an amount of 0.20% by mass or more based on a total amount of the lubricating oil composition.
 2. The lubricating oil composition according to claim 1, wherein a content of the component (A) is 0.01% by mass or more and 0.15% by mass or less based on the total amount of the lubricating oil composition.
 3. The lubricating oil composition according to claim 1, wherein a content of the component (B) is 0.05% by mass or more and 1.00% by mass or less based on the total amount of the lubricating oil composition.
 4. The lubricating oil composition according to claim 1, wherein, in formula (I), R² represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 8 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom.
 5. The lubricating oil composition according to claim 1, wherein, in formula (I), R¹ represents a hydrogen atom or a hydrocarbyl group having a number of carbon atoms of 1 or more and 5 or less that may contain at least one kind of an atom selected from the group consisting of an oxygen atom, a sulfur atom, and a nitrogen atom.
 6. The lubricating oil composition according to claim 1, wherein, formula (I), R² represents a hydrogen atom.
 7. The lubricating oil composition according to claim 1, wherein, in formula (I), R¹ represents a methyl group or a hydrogen atom.
 8. The lubricating oil composition according to claim 1, wherein the component (B) is at least one selected from the group consisting of an epoxy compound having a number of carbon atoms of 3 or more having a linear-chain or branched-chain alkyl group, and an alicyclic epoxy compound.
 9. The lubricating oil composition according to claim 1, wherein the component (B) is an alicyclic epoxy compound. 